'Sup bro, welcome to the forum...
Ok some more info is going to help here...
1st, are u using HPA (compressed air) or CO2?
2nd, are you shooting at 275 meters per second or is that feet per second? if my maths in right you could kill some one with 275mps!! For every one else, thats like 800+ fps!!
Ok Im not 100% on the Dragunfire, is it a blow back? IF so its a common answer, change the main spring... Also other than changing the input pressure is there another way of changeing velocity... check the manual there may well be. Eg some blowbacks like Spyders there is an adjuster at the back of the gun.
Sorry I cant say exactly how as I realy cant be asked to look up the Dragunfire.
On the barrel bit, you could try different paint... have a look at otters customs, url is something like:
www.otterscustoms.com have a look at the paint sizes and try find a bigger bore paint. Or get a new barrel... the steaths are nice, but I would rather get the J&J ceramic, the whole self cleaning thing does it for me
The url is:
http://www.ottersccustoms.com/